Dock levelers are often used to compensate for a height difference that can exist between a loading surface of a loading dock and the bed of a truck parked at the dock. A dock leveler system typically is mounted in a pit cut into the loading dock and includes a deck that is hinged at its back end to raise or lower the distal front end to generally match the height of the truck bed. A gap generally exists between the truck bed and the loading dock when the truck has backed up and is ready to be loaded or unloaded. An extension plate or lip can be pivotally coupled to the front end of the deck to bridge the gap. The deck and extended lip provide a path for a forklift truck or the like to travel from the loading dock onto the truck bed, thus facilitating loading or unloading of the truck.
If the bed of the truck is substantially at the same height as the floor of the loading dock, the deck elevation remains near a cross-traffic position. If the bed of the truck is higher than the loading dock floor, the deck can be rotated upward into an above dock position. It the bed of the truck is lower than the loading dock floor, the deck can be rotated into a below dock position. The deck can be used within a truck service range which is generally defined as a ±10% grade (or ±6° angularity).
As can be seen in FIG. 1, a typical dock leveling system 10 is shown in a stored position in a loading dock 12 of a building. In the stored position, also known as the cross-traffic position, the dock leveling system 10 is flush with the surrounding loading dock floor 13. The dock leveling system 10 is disposed in a pit 14 cut into the loading dock 12 and includes a deck 16 and a frame structure 18. The dock leveling system 10 defines a path indicated by arrows 20 that a forklift travels from the loading dock 12 into a truck to be loaded or unloaded. The deck 16 has a front end 22 and a back end 24, and the back end 24 defines a back edge 26 that extends the width of the deck 16. The deck 16 is strengthened by a plurality of stringers 28 that are approximately parallel to each other and run lengthwise from the front end 22 of the deck 16 to the back end 24. Extending downward from the back end 24 of the deck 16 are a plurality of extension members 30, each of which include a receiving hole 32. A deck 16 typically includes at least two pairs of extension members 30.
A lip 34 is connected to the front end 22 of the deck 16 by a lip hinge 36. The lip 34 is rotatable from a pendant position shown in FIG. 1 in which the lip 34 hangs downward, to an extended position in which the lip 34 extends substantially coplanar to the deck 16 and is able span the gap between the loading dock 12 and the bed of a truck to be unloaded.
The frame structure 18 includes a plurality of vertical uprights 38 upon each of which are disposed hinge members 40. The number of vertical uprights 38 generally corresponds to the number of pairs of extension members 30. Each hinge member 40 includes a hinge pin 42 disposed therethrough. Each hinge pin 42 also extends through a respective receiving hole 32 of one of the plurality of extension members 30, thereby rotatably connecting the deck 16 to the frame structure 18.
An upper member 41 is disposed on the hinge members 40. The upper member 41 can be a piece of angle iron and extend the entire width of the dock loading system 10. The upper member 41 includes a leading edge 43 opposite the back edge 26 of the deck 16.
Referring now to FIG. 2, the deck 16 is shown in the below-dock position. In this position, the deck 16 has been rotated about the hinge pins 42 so that the front end 22 of the deck 16 is lower than the back end 24. It is necessary to place the deck 16 in this position when the bed of a truck to be loaded or unloaded is lower than the floor of the loading dock 12.
As can be seen in FIG. 2, the back edge 26 of the back end 24 of the deck 16 extends rearwardly of the center of the hinge pins 42. Thus, when the front end 22 of the deck 16 is lowered, the back end 24 of the deck 16 is raised up a distance D1, thereby exposing the back edge 26 and creating an above dock floor projection 44 in the path 20 of a forklift traveling from the dock floor to the bed of a truck. Traveling over the projection 44 can be an annoyance to the driver of the forklift due to the amount of times the driver must enter and depart the truck in loading. The projection 44 can also cause damage to the wheels of the forklift. Furthermore, if a user is wheeling a hand truck into and out of the truck bed, the projection 44 can be difficult to overcome and cause jostling of the boxes being moved. In other situations, operators may be sliding skids along the ground into the truck. If an operator slides a skid into the exposed back edge 26, the skid cannot ride over the projection 44, and the skid can get damaged. This repeated impact can lead to damage of the rear hinge 40 of the dock leveling system 10.
Referring now to FIG. 3, the deck 16 is depicted in the above-dock position. In this example, the deck 16 can accommodate a truck that has a bed that is higher than the floor 13 of the loading dock 12. The deck 16 must then be rotated about the hinge pins 42 such that the front end 22 of the deck 16 is raised above the level of the bed of the truck. In this example, a hydraulic cylinder 46 is shown that can aid in the lifting and/or lowering of the deck 16.
Again, because the back edge 26 of the deck 16 extends rearwardly of the center of the hinge pins 42, when the front end 22 of the deck 16 is rotated upward, the back edge 26 is rotated down a distance D2, thus exposing the leading edge 43 of the upper member 41 of frame structure 18 and creating an above-deck projection 50 in the path 20 of the forklift. Again, when forklifts or skids exit towards the loading dock 12, they impact the exposed leading edge 43 of the upper member 41, possibly causing damage to the forklift wheels or the skids.
Assuming that there is no projection when the dock leveling system 10 is in the stored position, the prior art has attempted to reduce the projection 44 in the below dock position by changing the position of hinge members 40. If the hinge members 40 are lowered, the distance D1 will be lessened, and the projection 44 will be minimized. However, this will only exacerbate the projection 50 when the deck 16 is in the above-dock position. Because the hinge members 40 are lowered, when the deck 16 is in the above-dock position the distance D2 will be increased by the amount the hinge members 40 are lowered. The converse is also true in that if the hinge members 40 are raised, the projection 50 will be minimized in the above-dock position, but the projection 44 will be increased in the below dock position. Either approach does not produce a satisfactory solution.
For certain repairs to this type of dock leveler 10, the deck 16 can be rotated upward so that a technician can enter the pit 14 under the deck 16 and remove each of the individual hinge pins 42 from the extension members 30. In this manner, the deck 16 can be removed from the frame structure 18 to provide greater accessibility if required.
Another type of known dock leveling system, known as a Edge-of-Dock Leveler, or EOD, is depicted as structure 60 in FIG. 4. The EOD 60, described fully in U.S. Pat. No. 4,257,137, is fastened adjacent a loading dock 62 to the outside wall 64 of a building 66. The EOD 60 includes a mounting plate 68 fastened to the outside wall 64. The mounting plate 68 is connected to a deck 70 by a first piano hinge 72. In the piano hinge 72, as is known, a series of short tubes 74 extend from the top of the mounting plate 68 and are interengaged with a complementary series of short tubes 76 extending from the deck 70. The interengaged short tubes 74, 76 define a hollow tube that extends the width of the EOD 60. A rod (not shown) extends through the interengaged short tubes 74, 76 the width of the EOD 60 to define the first piano hinge 72. A lip plate 78 is connected to the deck 70 by a second piano hinge 80.
Extending outward from the building 66 on either side of the EOD 60 is a pair of bumper blocks 82. The bumper blocks 82 protect the building 66 from a truck that is backing up to the loading dock 62. The deck 70 and lip plate 78 are sized such that when the truck backs against the bumper blocks 82, the lip plate 78 can extend out into the bed of the truck.
In this situation, the first piano hinge 72 does not create a projection in the path of a forklift when the forklift is traveling into or out of the truck. However, due to the piano hinge construction and the bumper blocks 82 being placed on either side of the first piano hinge 72, the rod inside the first piano hinge 72 cannot be removed. Accordingly, the deck 70 cannot easily be removed to perform certain repairs or replacement.
Accordingly, it would be beneficial to provide a dock leveling system that does not create a projection in the path of a forklift, and further provides an easily removable deck for repair or replacement purposes.
While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and the equivalents falling within the spirit and scope of the invention as defined by the appended claims.